Attachments missing for group members

Please help!

I have many entries saved and each one has a pdf file attached to it. I shared the group with people and each of them have the “read and write” setting saved. When I first shared the group and invited the members, they were able to see all the attachments but now they are no longer showing up. The only thing the members can see is the bibliography section. The “read and write” setting is still the same and I don’t think I have changed anything else. What can I do to make the pdf attachments visible to every group member again?